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Extreme rainfall intensity is the mean intensity of events greater than or
equal to the 99th percentile each year, while extreme rainfall frequency is the mean
frequency of events greater than or equal to the 99th percentile each year.
I also briefly explained El Niño and La Niña phenomena, such that El Niño
normally brings dry weather and droughts, but could also bring extreme rains that
could trigger floods and landslides in some parts of the country like the 2009 flood
in Luzon brought by tropical storm Ondoy and the 2004 landslides in Real, Infanta
and Generak Nakar, Quezon. La Niña, on the other hand, stands for rainy weather
and floods. Example of this episode which exacerbated flooding was what
happened in Camarines Sur during typhoon Loleng in 1998. Also, in 2006 which
caused a landslide in Guinsaugon, Southern Leyte and deaths of at least 1,000
residents after strong rains for days. The rain was enhanced by the northeast
monsoon affected by the 2006 La Niña episode.
I also had a brief discussion on monsoons. Based on historical records, the
worst flood events were also due to southwest monsoons. Recently, however,
northeast monsoons also caused severe flooding.
Philippines has seen several climate- and weather-related events, like
tropical cyclones and monsoon rains, that have triggered hazards (floods and storm
surges), which proved disastrous. We recently had typhoons Yolanda (Haiyan),
Sendong (Washi), and Pablo (Bopha). These typhoons caused the highest number
of damages to properties and casualties.
Since the topic is really data-driven and technical, I agreed to the legal
representatives’ concern that interviewing me and documenting my answers in a
question and answer format may prove difficult due to the data and science
involved, thus, I provided them with my PowerPoint presentation (Annex “C”),
which I promised to present and elaborate on the day of the public hearing.
For added clarity, however, I am quoting below an excerpt or abstract of our
study “Long-term Trends and Extremes in Observed Daily Precipitation and Near
Surface Air Temperature in the Philippines for the Period 1951-2010”:
“Observed daily precipitation and near surface air temperature
data from 34 synoptic weather stations in the Philippines for the
period 1951–2010 were subjected to trend analysis which revealed an
overall warming tendency compared to the normal mean values for
the period 1961–1990. This warming trend can be observed in the
annual mean temperatures, daily minimum mean temperatures and to
a lesser extent, daily maximum mean temperatures. Precipitation and
temperature extremes for the period 1951–2010 were also analysed
relative to the mean 1961–1990 baseline values. Some stations
(Cotabato, Iloilo, Laoag and Tacloban,) show increases in both